Fix long error messages breaking InfoLog::append.
Fix long error messages breaking InfoLog::append.

Using two calls to vsnprintf allows us to correctly determine
maximum buffer size as well as fixing garbage characters from
a missing NULL terminator.

Bug report from roland@lagoa.com.

BUG=angle:561

Change-Id: I4eb156342d9106d40783a3cf57c0c1d1889390e2
Reviewed-on: https://chromium-review.googlesource.com/186988
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@chromium.org>
Reviewed-by: Shannon Woods <0f3694938fd5703bd548127ee497e4d604509bef@chromium.org>
Tested-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

crezefire/angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,mlfarrell/angle,vvuk/angle,ppy/angle,mybios/angle,ppy/angle,mybios/angle,ecoal95/angle,xin3liang/platform_external_chromium_org_third_party_angle,xin3liang/platform_external_chromium_org_third_party_angle,ecoal95/angle,MSOpenTech/angle,jgcaaprom/android_external_chromium_org_third_party_angle,mikolalysenko/angle,bsergean/angle,mlfarrell/angle,jgcaaprom/android_external_chromium_org_third_party_angle,crezefire/angle,nandhanurrevanth/angle,mrobinson/rust-angle,larsbergstrom/angle,csa7mdm/angle,mikolalysenko/angle,android-ia/platform_external_chromium_org_third_party_angle,jgcaaprom/android_external_chromium_org_third_party_angle,larsbergstrom/angle,mybios/angle,android-ia/platform_external_chromium_org_third_party_angle,jgcaaprom/android_external_chromium_org_third_party_angle,csa7mdm/angle,bsergean/angle,android-ia/platform_external_chromium_org_third_party_angle,MIPS/external-chromium_org-third_party-angle,ghostoy/angle,MIPS/external-chromium_org-third_party-angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,mikolalysenko/angle,nandhanurrevanth/angle,bsergean/angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,MSOpenTech/angle,ghostoy/angle,domokit/waterfall,xin3liang/platform_external_chromium_org_third_party_angle,larsbergstrom/angle,vvuk/angle,ecoal95/angle,mlfarrell/angle,mrobinson/rust-angle,MSOpenTech/angle,crezefire/angle,geekboxzone/lollipop_external_chromium_org_third_party_angle,mrobinson/rust-angle,csa7mdm/angle,domokit/waterfall,csa7mdm/angle,android-ia/platform_external_chromium_org_third_party_angle,MIPS/external-chromium_org-third_party-angle,vvuk/angle,mikolalysenko/angle,nandhanurrevanth/angle,vvuk/angle,ghostoy/angle,mrobinson/rust-angle,crezefire/angle,ecoal95/angle,ghostoy/angle,MSOpenTech/angle,mrobinson/rust-angle,bsergean/angle,mybios/angle,nandhanurrevanth/angle,MIPS/external-chromium_org-third_party-angle,xin3liang/platform_external_chromium_org_third_party_angle,ppy/angle,larsbergstrom/angle,ppy/angle,ecoal95/angle,mlfarrell/angle